Polymer seal assembly

ABSTRACT

A seal assembly includes a seal body, a spring disposed adjacent to the seal body, and a seal ring disposed adjacent to the seal body. The seal body and the seal ring can include a plastic polymer material. The seal assembly can be a subcomponent of hydraulic strut in the landing gear of an aircraft.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional and claims priority under 35 U.S.C. §120 to U.S. patent application Ser. No. 14/755,407 entitled, “POLYMERSEAL ASSEMBLY,” by Lenhert et al., filed Jun. 30, 2015, whichapplication claims priority under 35 U.S.C. § 119(e) to U.S. ProvisionalApplication No. 62/022,480 entitled “POLYMER SEAL ASSEMBLY,” by Lenhertet al., filed Jul. 9, 2014, of which all are assigned to the currentassignee hereof and incorporated herein by reference in theirentireties.

FIELD OF THE DISCLOSURE

The present disclosure relates in general to seals and, in particular,to improved systems, methods, and apparatuses for a spring-energizedpolymer dynamic seal assembly.

RELATED ART

Dynamic seals for linear motion rods or cylinders that are used inhydraulic service prevent the loss of hydraulic fluid from the systemand the intrusion of foreign particles between the moving parts.Conventional dynamic seals used, for example, as a subcomponent of thelanding gear of an aircraft typically comprise elastomers for itsdeformability and resilience. However, elastomers wear quickly and areprone to tear, thus requiring frequent replacement. In additionelastomers can become hard, stiff, and brittle when exposed to lowtemperatures and, thus, can malfunction. Thus, a need exists for animproved linear dynamic seal.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example and are not limited in theaccompanying figures.

FIG. 1 includes an illustration of cross-section of an embodiment of theseal assembly described herein.

FIG. 2 includes an illustration of a cross-section of an embodiment of asystem for linear movement described herein.

Skilled artisans appreciate that elements in the figures are illustratedfor simplicity and clarity and have not necessarily been drawn to scale.For example, the dimensions of some of the elements in the figures maybe exaggerated relative to other elements to help to improveunderstanding of embodiments of the invention.

DETAILED DESCRIPTION

The following description in combination with the figures is provided toassist in understanding the teachings disclosed herein. The followingdiscussion will focus on specific implementations and embodiments of theteachings. This focus is provided to assist in describing the teachingsand should not be interpreted as a limitation on the scope orapplicability of the teachings. However, other embodiments can be usedbased on the teachings as disclosed in this application.

The terms “comprises,” “comprising,” “includes,” “including,” “has,”“having” or any other variation thereof, are intended to cover anon-exclusive inclusion. For example, a method, article, or apparatusthat comprises a list of features is not necessarily limited only tothose features but may include other features not expressly listed orinherent to such method, article, or apparatus. Further, unlessexpressly stated to the contrary, “or” refers to an inclusive-or and notto an exclusive-or. For example, a condition A or B is satisfied by anyone of the following: A is true (or present) and B is false (or notpresent), A is false (or not present) and B is true (or present), andboth A and B are true (or present).

Also, the use of “a” or “an” is employed to describe elements andcomponents described herein. This is done merely for convenience and togive a general sense of the scope of the invention. This descriptionshould be read to include one, at least one, or the singular as alsoincluding the plural, or vice versa, unless it is clear that it is meantotherwise. For example, when a single item is described herein, morethan one item may be used in place of a single item. Similarly, wheremore than one item is described herein, a single item may be substitutedfor that more than one item.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. The materials, methods, andexamples are illustrative only and not intended to be limiting. To theextent not described herein, many details regarding specific materialsand processing acts are conventional and may be found in textbooks andother sources within the sealing arts.

Embodiments of the seal assembly according to the present disclosure aremore durable than a conventional elastomer seal assembly. In addition,embodiments of the seal assembly described herein can have an improvedsealing capacity as compared to a conventional seal assembly. Theconcepts are better understood in view of the embodiments describedbelow that illustrate and do not limit the scope of the presentinvention

Referring now to FIG. 1, in certain embodiments, the seal assembly 10can comprise a radial seal assembly. In particular embodiments, the sealassembly 10 can comprise three components: a seal body 20, a spring 30disposed adjacent to the seal body 20, and a seal ring 40 disposedadjacent to the seal body 20. In other embodiments, the seal assemblycan include only the seal body 20 and the spring 30.

The seal body 20 can have an annular shape that is concentric with thespring 30 and the seal ring 40. The seal body 20 can have a firstportion having a generally rectangular cross-section and a secondportion having a generally U-shaped cross-section. The seal body 20 canhave a major surface 21 adapted to face a shaft or rod such that atleast a portion of the major surface 21 engages with the shaft or rodsurface to form a seal.

The major surface 21 can define an inner diameter of the seal body 20.In certain embodiments, the seal body 20 can have an inner diameter ID₁of at least 80 mm, at least 85 mm, or at least 90 mm. In furtherembodiments, the seal body 20 can have an inner diameter ID₁ of nogreater than 150 mm, no greater than 125 mm, or no greater than 115 mm.In yet further embodiments, the seal body 20 can have an inner diameterID₁ in a range of any of the above maximum or minimum values, such as ina range of 80 to 150 mm, 85 to 125 mm, or 90 to 115 mm.

The major surface 21 can include at least one seal groove 23 thatextends radially along the major surface 21 of the seal body 20. Incertain embodiments, the at least one seal groove 23 can have opposingasymmetric sidewalls 25, 27 that extend into the thickness of the sealbody 20. In particular embodiments, the major surface 21 of the sealbody 20 can include a plurality of repeating seal grooves 23, eachhaving opposing asymmetric sidewalls 25, 27 that extend into thethickness of the seal body 20.

The seal body 20 can include a major surface 29 that is opposed to themajor surface 21 and defines an outer diameter of the seal body 20. Thedistance between the major surface 21 and the major surface 29 can bereferred to as the radial height RH₁ of the seal body 20. In certainembodiments, the seal body 20 can have a radial height RH₁ of at least 1mm, at least 2 mm, or at least 4 mm. In further embodiments, the sealbody 20 can have a radial height RH₁ of no greater than 12 mm, nogreater than 10 mm, or no greater than 8 mm. In yet further embodiments,the seal body 20 can have a radial height R_(H1) in a range of any ofthe above minimum and maximum values, such as in a range of 1 to 12 mm,2 to 10 mm, or 4 to 8 mm.

In certain embodiments, the seal body 20 can have an RH₁:ID₁ ratio of atleast 1:30, at least 1:25, at least 1:20, or at least 1:15. In furtherembodiments, the seal body can have an RH₁:ID₁ ratio of no greater than1:5, no greater than 1:7, or no greater than 1:10. In yet furtherembodiments, the seal body can have an RH₁:ID₁ ratio in a range of anyof the above minimum and maximum values, such as in a range of 1:30 to1:5, 1:25 to 1:7, or 1:20 to 1:10.

The seal body 20 can include a contact surface 24 that can define anaxial end of the seal body. In certain embodiments, the contact surface24 can be adapted to contact the seal ring 40. In particularembodiments, the seal body 20 and the seal ring 40 are not adhered toeach other, but are separate components.

In certain embodiments, the contact surface 24 can be a substantiallyflat surface. In a particular embodiment, the contact surface 24 can liealong a plane that is substantially orthogonal to a central axis of theseal body 20. As illustrated in FIG. 1, the at least one seal groove 23discussed previously can be located in a region near the contact surface24.

The axial height AH₁ of the seal body 20 can be defined as the maximumdistance from the contact surface 24 to the opposing axial end of theseal body 20. In certain embodiments, the seal body 20 can have an axialheight AH₁ of at least 2 mm, at least 4 mm, or at least 6 mm. In furtherembodiments, the seal body 20 can have an axial height AH₁ of no greaterthan 14 mm, no greater than 12 mm, or no greater than 10 mm. In yetfurther embodiments, the seal body 20 can have an axial height AH₁ in arange of any of the above minimum and maximum values, such as in a rangeof 2 to 14 mm, 4 to 12 mm, or 6 to 10 mm.

In certain embodiments, the total axial height AH_(T) of the sealassembly 10 can be equal to the sum of the axial height AH₁ of the sealbody 20 and the axial height AH₂ of the seal ring 40, and seal ring 40will be described in more detail later. In other embodiments, such as,for example, where the seal assembly 10 does not include the seal ring40, the total axial height AH_(T) of the seal assembly 10 is equal tothe axial height AH₁ of the seal body 20. In particular embodiments, theseal assembly can have a total axial height AH_(T) of at least 6 mm, atleast 7 mm, at least 8 mm, or at least 9 mm. In further embodiments, thetotal axial height AH_(T) of the seal assembly is no greater than 20 mm,no greater than 15 mm, or no greater than 11 mm. In yet furtherembodiments, the total axial height AH_(T) of the seal assembly can bein a range of any of the above minimum and maximum values, such as in arange of 6 to 20 mm, 7 to 15 mm, or 8 to 11 mm.

The seal body 20 can be formed of a polymer material. In certainembodiments, the polymer material can include a plastic polymermaterial. In particular embodiments, the seal body 20 can be aplastic-based seal body, separate and distinct from an elastomer-basedseal. For example, the seal body 20 can be free of a silicone elastomeror free of any elastomer. As used herein, a plastic polymer material isdistinct from and does not encompass an elastomer material. An elastomermaterial is a natural or synthetic polymer, e.g. rubber, recognized forits viscoelastic properties.

For example, the plastic polymer material can have a Young's Modulus ofat least 150 MPa, at least 200 MPa, at least 250 MPa, or at least 300MPa. The plastic polymer material may have a Young's Modulus of nogreater than 1500 MPa, no greater than 1000 MPa, or no greater than 800MPa. The plastic polymer material can have a Young's Modulus in therange of any of the above minimums and maximums, such as in a range of150 to 1500 MPa, 200 to 1000 MPa, or 300 to 800 MPa.

In certain embodiments, the seal body 20 can have a Shore D Hardness ofat least 50, at least 55, or at least 60. In further embodiments, theseal body 20 can have a Shore D Hardness of no greater than 75, nogreater than 73, or no greater than 70. In yet further embodiments, theseal body 20 can have a Shore D Hardness in a range of any of the aboveminimum and maximum values, such as 50 to 75, 55 to 73, or 60 to 70.

The plastic polymer material can include a nylon, a fluoroplastic, apolybenzimidazole (PBI), a polyether ether ketone (PEEK), apolyaryletherketone (PAEK), a polyimide (PI), or any combinationthereof. In a particular embodiment, the polyimide can include apolyetherimide (PEI). In another particular embodiment, the plasticpolymer material can include a fluoroplastic. The fluoroplastic caninclude a polytetrafuoroethylene (PTFE), a perfluoroalkoxy (PFA), afluorinated ethylene propylene (FEP), a modified PTFE (TFM), an ethylenetetrafluoroethylene (ETFE), a polychlorotrifluoroethene (PCTFE), or anycombination thereof. In certain embodiments, the polymer material caninclude a liquid crystal polymer.

Conventionally, elastomer based seals have been required for certainapplications, such as the hydraulic strut of an aircraft landing gear,that include a seal with a large radial height relative to its innerdiameter. The seal assembly is conventionally installed via the lowpressure/atmospheric side of the hydraulic strut. However, hydraulicstruts can include several grooves and sharp edges in the bore on thelow pressure/atmospheric side of the hydraulic strut, adjacent thegroove where the seal is to be installed. Plastic polymer based seals inapplications having the above radial height to inner diameter ratio wereconventionally considered too stiff to manipulate in the narrow bore tobypass the grooves and sharp edges, and install without causing damageto the seal. Still, the deformation and resilience of elastomer basedseals allow for large radial height seal bodies to be manipulated in thenarrow bore and bypass the grooves and sharp edges with minimal damage.However, the load/deflection and glass transition characteristics ofelastomers do not make optimal seals for certain dynamic sealapplications, such as hydraulic struts for aircraft landing gear.Elastomers can shrink and/or become brittle when an aircraft is at acruising altitude of, e.g., 35,000 feet because of the low temperatures,e.g. less than −40° C. When the aircraft descends in an attempt to land,there may not be sufficient time for the elastomer to return to itselastic state necessary for proper operation of the landing gear beforethe aircraft needs to land. In addition, an elastomer can deform underintense pressure such that it can be difficult to keep the seal on theshaft at all times, increasing the leakage rate of the seal. Also,elastomers can be prone to tearing or high wear rates, increasingleakage rate and frequency of replacement.

Applicants have concurrently developed unique installation methods andtooling that allow for installation of a seal body including a plasticpolymer material that limits or avoids such damage during installation.Accordingly, another aspect of the present disclosure is directed to amethod of installing a seal body, which will be described later in thisdisclosure.

As stated previously, the seal assembly 10 can include components inaddition to the seal body 20. For example, as illustrated in FIG. 1, theseal body 20 can include a spring 30 adjacent to the seal body 20, suchas disposed in the seal body 20, such as disposed in the second portionof the seal body 20 having a U-shaped cross-section. The spring 30 canbe adapted to bias a radial portion of the seal body 20 into radialcontact with a housing and to bias another radial portion of the sealbody 20 into radial contact with a shaft for providing a dynamic sealtherebetween.

In certain embodiments, the spring 30 can be disposed in an annularopening of the seal body 20 in an axial direction. In particularembodiments, the spring 30 can have an apex that abuts an inner, concavesurface the annular opening of the seal body 20. The spring 30 can begenerally free of direct contact with the seal ring 40.

In certain embodiments, the spring can include a metal material. Inparticular embodiments, the spring can be die-formed from an overlappedmetal strip and configured with U-shaped cantilevers.

Further, another component of the seal assembly 10 can include a sealring 40 disposed adjacent to the contact surface 24 of the seal body 20.In certain embodiments, the seal ring 40 can be concentric with the sealbody 20. As illustrated in FIGS. 1 and 2, the seal ring 40 can have agenerally rectangular cross-section. The cross-section of the seal ring40 can have other shapes depending on the intended application.

In certain embodiments, the seal ring 40 can have a major surface 41that can engage, or be adapted to engage a shaft or rod to form a seal.The major surface 41 can define an inner diameter ID₂ of the seal ring40. In certain embodiments, the seal ring can have an inner diameter ID₂of at least 80 mm, at least 85 mm, at least 90 mm. In furtherembodiments, the seal ring 40 can have an inner diameter ID₂ of nogreater than 150 mm, no greater than 125 mm, or no greater than 115 mm.In even further embodiments, the seal ring 40 can have an inner diameterID₂ in a range of any of the above minimum and maximum values, such asin a range of 80 to 150 mm, 85 to 125 mm, or 90 to 115 mm. The innerdiameter ID₂ of the seal ring 40 can be the same as or different thanthe inner diameter ID₁ of the seal body 20. In certain embodiments, ID₁is substantially the same as ID₂.

The seal ring 40 can include a major surface 49 that is opposed to themajor surface 41 and defines an outer diameter of the seal ring 40. Thedistance between the major surface 41 and the major surface 49 can bereferred to as the radial height RH₂ of the seal ring 40. In certainembodiments, the seal ring 40 can have a radial height RH₂ of at least 1mm, at least 2 mm, or at least 4 mm. In further embodiments, the sealring 40 can have a radial height RH₂ of no greater than 12 mm, nogreater than 10 mm, or no greater than 8 mm. In yet further embodiments,the seal ring 40 can have a radial height RH₂ in a range of any of theabove maximum and minimum values, such as in a range of 1 to 12 mm, 2 to10 mm, or 4 to 8 mm. The radial height RH₂ of the seal ring 40 can bethe same or different than the radial height RH₁ of the seal body 20. Ina particular embodiment, RH₂ can be substantially the same as RH₁.

The major surface 41 can include at least one seal ring groove 43 thatextends radially along the major surface 41 of the seal ring 40. Incertain embodiments, the at least one seal ring groove 43 can haveopposing asymmetric sidewalls 45, 47 that extend into the thickness ofthe seal ring 40. In particular embodiments, the major surface 41 caninclude a plurality of seal ring grooves, each having asymmetricsidewalls 45, 47 that extend into the thickness of the seal ring 40. Ina more particular embodiment, each of the plurality of seal ring grooves43 can have bilateral symmetry with each other.

In certain embodiments, the seal ring 40 can have a contact surface 44that faces, abuts, or even directly contacts the contact surface 24 ofthe seal body 20. In particular embodiments, the contact surface 44 ofthe seal ring 40 can be substantially orthogonal to a central axis ofthe seal ring 40. The contact surface 44 of the seal ring 40 can havesubstantially the same dimensions as the contact surface 24 of the sealbody.

The axial height AH₂ of the seal ring 40 can be defined as the maximumdistance from the contact surface 44 to the opposing axial end of theseal ring 40. In certain embodiments, the seal ring 40 can have an axialheight A_(H2) of at least 1 mm, at least 1.5 mm, or at least 2 mm. Infurther embodiments, the seal ring 40 can have an axial height AH₂ of nogreater than 6 mm, no greater than 5 mm, or no greater than 4 mm. In yetfurther embodiments, the seal ring 40 can have an axial height AH₂ in arange of any of the above maximum and minimum values, such as in a rangeof 1 to 6 mm, 1.5 to 5 mm, or 2 to 4 mm.

The seal ring 40 can include a plastic polymer material. The plasticpolymer material can include one or more of the plastic polymermaterials listed above for the seal body 20. The seal ring 40 can befree of an elastomer.

In certain embodiments, the seal ring 40 can have a Shore D Hardness ofat least 47, at least 53, or at least 57. In further embodiments, theseal ring 40 can have a Shore D Hardness of no greater than 73, nogreater than 70, or no greater than 67. In yet further embodiments, theseal body 20 can have a Shore D Hardness in a range of any of the aboveminimum and maximum values, such as 47 to 73, 53 to 70, or 57 to 67.

In certain embodiments, the seal ring 40 can be made from the samematerial as the seal body 20. Although the dynamics of the seal ring 40can be different than the dynamics of the seal body 20, the seal body 20and the seal ring 40 can work best in certain applications when madefrom the same material.

In certain embodiments, the seal ring 40 can be made from a materialthat is different than the material used for the seal body 20. In aparticular embodiment, the seal ring 40 can be made of a material thathas a durometer hardness that is less than the durometer hardness of theseal body 20. For example, the difference between the Shore D Hardnessvalue for the seal ring 40 and the Shore D Hardness value for the sealbody 20 can be at least 1, at least 3, or at least 5. In furtherembodiments, the difference between the Shore D Hardness value for theseal ring 40 and the Shore D Hardness value for the seal body 20 may beno greater than 20, no greater than 15, or no greater than 10. In yetfurther embodiments, the difference between the Shore D Hardness valuefor the seal ring 40 and the Shore D Hardness value for the seal body 20can be in a range of any of the above minimum and maximum values, suchas 1 to 20, 3 to 15, or 5 to 10.

The seal assembly 10 can be a dynamic seal assembly for, e.g., linearmotion applications, such as the system 100 illustrated in FIG. 2. Asillustrated, system 100 can include a housing 150 having a bore 153 withan axis 155, and a gland or recess 160 located in the bore 153. A rod170 can be coaxially located in the bore 153 for axial motion relativeto housing 150. The rod 170 can have an outer surface 173 comprising adynamic surface relative to housing 150, which has a static surface 157in the embodiment shown.

The seal assembly 10 can be located, or adapted to be located, in therecess 160 of the bore 153. The seal assembly 10 can form, or be adaptedto form, a seal between the housing 150 and the rod 170. In particularembodiments, the spring 30 can be installed, or adapted to be installed,in the seal body 20 such that the spring 30 biases certain radialportions of the seal body 20 into radial contact with both the housing150 and the rod 170 for providing a dynamic seal therebetween. In otherembodiments, the seal assembly 10 may be configured as a face seal whichare commonly used to seal between parallel flat surfaces, swivelcouplings and flange-type joints, for example.

In certain embodiments, the seal assembly can be a hydraulic strut sealassembly for aircraft landing gear. That is, the seal assembly can be anaircraft landing gear subcomponent. The hydraulic strut seal assemblycan provide a dynamic seal between a housing and a shaft of a hydraulicstrut. In certain embodiments, the dynamic seal having a leakage rate ofno greater than 0.05 mL per simulated flight cycle for at least 2000simulated flight cycles, at least 3000 simulated flight cycles, at least4000 simulated flight cycles, at least 5000 simulated flight cycles, atleast 10000 simulated flight cycles, at least 15000 simulated flightcycles, or at least 20000 flight cycles, according to a Flight CycleTest. The Flight Cycle Test can be performed on a linear actuator testbed including a test bed strut, a test seal at one end of the strut, anda tool seal at the other end of the strut. A simulated flight cycle ofthe Flight Cycle Test includes a series of phases that simulates thedifferent environments in which the seal will need to operate. Theseries of phases includes a taxi phase that simulates taxiing andwaiting at the beginning of the runway, a take-off phase that simulatesa take-off run and an effective take-off, an effective flight phase thatsimulates shock absorbers extended during flight, a landing phase thatsimulates landing, braking, ending of braking, taxiing, and parking, arest phase, and a towing phase. As used herein, a seal assembly isconsidered to have completed one simulated flight cycle of the FlightCycle Test after completing each of these phases once. The details ofeach phase of a flight cycle of the Flight Cycle Test are included inTable 1.

TABLE 1 TOTAL STROKE FREQ AMPLITUDES PRESSURE TIME STROKE PHASE MMDESCRIPTION Hz mm Bars Sec (mm) 6  0 to 390 Landing N/A  19.5 TO 188.40.8 390 7 390 Braking 4  ±7.5 mm 188.4 (+29/−22.2)   20 2400 Transition1 30 8 360 End of Braking 1 ±40  118.8 (+108.8/−41.6) 4 640 9 360 Taxi 2±735 mm 188.4 (+13.1/−10.4) 180 10800 10 360 Parking 118.8 15 0 11 360Rest on 118.8 180 0 Ground Transition 1 10 12 370 Towing 136.3 10 0 1370 Taxi 2   ±7.5 136.3 (+16.9/−13.1) 270 16200 2 370 Waiting @ 136.3 30 Beginning of Runway 3 370 to 230 Take Off Run 136.3 to 42.4 36 140 4230 to 0  Effective  42.4 to 19.5 1.3 230 Take Off 5  0 Shock  19.5 1890 Absorber Extended During Flight

Further, as stated previously, Applicants have developed uniqueinstallation methods and tooling that allow for installation of a sealbody including a plastic polymer material that limits or avoids suchdamage during installation. The method of installing the seal bodydescribed herein can include providing a housing having a bore with anaxis and a blind recess located in the bore; disposing a plastic polymerseal assembly in the blind recess of the bore; and disposing a shaft inthe bore for axial motion relative thereto. The installation method canfurther include providing an installation tool set including a sleeve, aplug, and a pusher. The seal body can be compressed into an oval shapeand inserted into the sleeve. The pusher can be inserted into the sleeveand the seal body can be pushed against the plug until the seal body isdisposed in the recess of the bore of the housing.

The present disclosure represents a departure from the state of the art.For example, it was previously unknown how to provide a seal assemblyfor applications such as aircraft landing gear where the seal and thebackup ring are made of a plastic polymer material. In addition, it waspreviously unknown how to install an all-plastic seal having a ratio ofradial height to inner diameter of at least 1:20, such as those used inaircraft landing gear. In addition, the sealing assembly described abovecan demonstrate a synergistic improvement in the combination of numberof flight cycles and leakage rate per flight cycles, as illustrated inthe following non-limiting examples. Further, Applicants haveconcurrently developed unique installation methods and tooling thatallow for installation of a seal body including a plastic polymermaterial that limits or avoids such damage during installation.

Many different aspects and embodiments are possible. Some of thoseaspects and embodiments are described below. After reading thisspecification, skilled artisans will appreciate that those aspects andembodiments are only illustrative and do not limit the scope of thepresent invention. Embodiments may be in accordance with any one or moreof the items as listed below.

Item 1. A seal assembly comprising:

a seal body comprising a first material;

a spring disposed adjacent to the seal body; and

a seal ring comprising a second material,

wherein each of the first material and the second material comprises aplastic polymer material having a Young's modulus of at least 150 MPa.

Item 2. A seal assembly comprising:

a seal body comprising a first material;

a spring disposed adjacent to the seal body; and

a seal ring comprising a second material,

wherein the first material and the second material have the samecomposition.

Item 3. A hydraulic strut seal assembly adapted to provide a dynamicseal between a housing and a shaft of a hydraulic strut, the dynamicseal having a leakage rate of no greater than 0.05 mL per simulatedflight cycle for at least 2000 simulated flight cycles according to aFlight Cycle Test.

Item 4. A system for linear motion, comprising:

a housing having a bore with an axis and a blind recess located in thebore;

a shaft located in the bore for axial motion relative thereto;

a seal assembly comprising a plastic polymer material located in theblind recess of the bore adapted to provide a dynamic seal between thehousing and the shaft,

wherein the ratio of a radial height RH₁ of the seal assembly to aninner diameter of the seal assembly is less than 1:20.

Item 5. A method of installing a seal assembly, comprising

providing a housing having a bore with an axis and a blind recesslocated in the bore;

disposing a seal assembly comprising a plastic polymer material in theblind recess of the bore;

disposing a shaft in the bore for axial motion relative thereto;

wherein the ratio of a radial height of the seal assembly to an innerdiameter of the seal assembly is less than 1:20.

Item 6. The sealing assembly, system, or method of any one of items 3-5,wherein the seal assembly includes:

a seal body comprising a first material; and

a spring disposed adjacent to the seal body.

Item 7. The sealing assembly, system or method of item 6, wherein theaxial height of the seal body AH₁ is equal to the total axial heightAH_(T) of the seal assembly.

Item 8. The sealing assembly, system or method of item 6, wherein theseal assembly further includes a seal ring comprising a second material,wherein (1) each of the first and second materials comprises a plasticpolymer material having a Young's modulus of at least 150 MPa or (2) thefirst and second materials are the same.

Item 9. The seal assembly, system, or method of any one of the precedingitems, wherein the first material comprises a nylon, a fluoroplastic, apolybenzimidazole (PBI), a polyether ether ketone (PEEK), apolyaryletherketone (PAEK), a polyimide (PI), or any combinationthereof.

Item 10. The seal assembly, system, or method of any one of thepreceding items, wherein the first material comprises a polyetherimide(PEI).

Item 11. The seal assembly, system, or method of any one of thepreceding items, wherein the first material comprises a liquid crystalpolymer.

Item 12. The seal assembly, system, or method of any one of thepreceding items, wherein the first material comprises a fluoroplastic.

Item 13. The seal assembly, system, or method of item 12, wherein thefluoroplastic includes a polytetrafuoroethylene (PTFE), aperfluoroalkoxy (PFA), a fluorinated ethylene propylene (FEP), amodified PTFE (TFM), an ethylene tetrafluoroethylene (ETFE), apolychlorotrifluoroethene (PCTFE), or any combination thereof.

Item 14. The seal assembly, system, or method of any one of thepreceding items, wherein the first material has a Young's Modulus of atleast 150 MPa, at least 200 MPa, at least 250 MPa, or at least 300 MPa.

Item 15. The seal assembly, system, or method of any one of thepreceding items, wherein the first material has a Young's Modulus of nogreater than 1500 MPa, no greater than 1000 MPa, or no greater than 800MPa.

Item 16. The seal assembly, system, or method of any one of thepreceding items, wherein the first material has a Young's Modulus in arange of 150 to 1500 MPa, 200 to 1000 MPa, or 300 to 800 MPa.

Item 17. The seal assembly, system, or method of any one of thepreceding items, wherein the second material comprises a nylon, afluoroplastic, a PBI, a PEEK, a PAEK, a PI, or any combination thereof.

Item 18. The seal assembly, system, or method of any one of thepreceding items, wherein the second material comprises a polyetherimide(PEI).

Item 19. The seal assembly, system, or method of any one of thepreceding items, wherein the second material comprises a liquid crystalpolymer.

Item 20. The seal assembly, system, or method of any one of thepreceding items, wherein the second material comprises a fluoroplastic.

Item 21. The seal assembly, system, or method of item 20, wherein thefluoroplastic includes a PTFE, a PFA, a FEP, a TFM, an ETFE, a PCTFE, orany combination thereof.

Item 22. The seal assembly, system, or method of any one of thepreceding items, wherein the second material has a Young's Modulus of atleast 150 MPa, at least 200 MPa, at least 250 MPa, or at least 300 MPa.

Item 23. The seal assembly, system, or method of any one of thepreceding items, wherein the second material has a Young's Modulus of nogreater than 1500 MPa, no greater than 1000 MPa, or no greater than 800MPa.

Item 24. The seal assembly, system, or method of any one of thepreceding items, wherein the second material has a Young's Modulus in arange of 150 to 1500 MPa, 200 to 1000 MPa, or 300 to 800 MPa.

Item 25. The seal assembly, system, or method of any one of thepreceding items, wherein the first material and the second material arethe same.

Item 26. The seal assembly, system, or method of any one of thepreceding items, wherein the first material and the second material aredifferent.

Item 27. The seal assembly, system, or method of any one items 1-24 and26, wherein wherein the Shore D Hardness of the second material is lessthan the Shore D Hardness of the first material.

Item 28. The seal assembly, system, or method of item 27, wherein thedifference in Shore D Hardness values is at least 1, at least 3, or atleast 5.

Item 29. The seal assembly, system, or method of items 27 or 28, whereinthe difference in Shore D Hardness values is no greater than 20, nogreater than 15, or no greater than 10.

Item 30. The seal assembly, system, or method of any one of items 27-29,wherein the difference in Shore D Hardness values is in a range of 1 to20, 3 to 15, or 5 to 10.

Item 31. The seal assembly, system, or method of any one of thepreceding items, wherein the first material is free of an elastomer, thesecond material is free of an elastomer, or both the first material andthe second material are free of an elastomer.

Item 32. The seal assembly, system, or method of any one of thepreceding items, wherein the total axial height AH_(T) of the sealassembly is at least 6 mm, at least 7 mm, at least 8 mm, or at least 9mm.

Item 33. The seal assembly, system, or method of any one of thepreceding items, wherein the total axial height AH_(T) of the sealassembly is no greater than 20 mm, no greater than 15 mm, or no greaterthan 11 mm.

Item 34. The seal assembly, system, or method of any one of thepreceding items, wherein the total axial height AH_(T) of the sealassembly in a range of 6 to 20 mm, 7 to 15 mm, or 8 to 11 mm.

Item 35. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has an annular shape.

Item 36. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body is concentric with the seal ring.

Item 37. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body includes a first portion having agenerally rectangular cross-section and a second portion having agenerally U-shaped cross-section.

Item 38. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has an inner diameter ID₁ of 80mm, at least 85 mm, or at least 90 mm.

Item 39. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has an inner diameter ID₁ of nogreater than 150 mm, no greater than 125 mm, or no greater than 115 mm.

Item 40. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has an inner diameter ID₁ in arange of 80 to 150 mm, 85 to 125 mm, or 90 to 115 mm.

Item 41. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has a radial height RH₁ of atleast 1 mm, at least 2 mm, or at least 4 mm.

Item 42. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has a radial height RH₁ of nogreater than 12 mm, no greater than 10 mm, or no greater than 8 mm.

Item 43. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has a radial height RH₁ in arange of 1 to 12 mm, 2 to 10 mm, or 4 to 8 mm.

Item 44. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has a ratio of radial height RH₁to inner diameter ID₁ of at least 1:30, at least 1:25, at least 1:20, orat least 1:15.

Item 45. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has a ratio of radial height RH₁to inner diameter ID₁ of no greater than 1:5, no greater than 1:7, or nogreater than 1:10.

Item 46. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has a ratio of radial height RH₁to inner diameter ID₁ in a range of 1:30 to 1:5, 1:25 to 1:7, or 1:20 to1:10.

Item 47. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has a first major surfacedefining an inner diameter, the first major surface adapted to engage ashaft and perform a sealing function.

Item 48. The seal assembly, system, or method of item 43, wherein thefirst major surface of the seal body includes at least one seal groovethat extends radially along the first major surface of the seal ring.

Item 49. The seal assembly, system, or method of item 44, wherein the atleast one seal groove has opposing asymmetric sidewalls that extend intothe thickness of the seal body.

Item 50. The seal assembly, system, or method of any one of items 43-45,wherein the first major surface of the seal body includes at least tworepeating seal grooves having opposing asymmetric sidewalls that extendinto the thickness of the seal body.

Item 51. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has a contact surface that facesthe seal ring.

Item 52. The seal assembly, system, or method of item 47, wherein thecontact surface of the seal body is substantially orthogonal to acentral axis of the seal body.

Item 53. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has an axial height AH₁ of atleast 2 mm, at least 4 mm, or at least 6 mm.

Item 54. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has an axial height AH₁ of nogreater than 14 mm, no greater than 12 mm, or no greater than 10 mm.

Item 55. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has an axial height AH₁ in arange of 2 to 14 mm, 4 to 12 mm, or 6 to 10 mm.

Item 56. The seal assembly, system, or method of any one of thepreceding items, wherein the spring is adapted to bias a first radialportion of the seal body into radial contact with a housing and to biasa second radial portion of the seal body into radial contact with ashaft for providing a dynamic seal therebetween.

Item 57. The seal assembly, system, or method of any one of thepreceding items, wherein the spring is free of direct contact with theseal ring.

Item 58. The seal assembly, system, or method of any one of thepreceding items, wherein the spring is disposed in an annular opening ofthe seal body in an axial direction.

Item 59. The seal assembly, system, or method of item 54, wherein thespring has an apex that abuts an inner, concave surface the annularopening of the seal body.

Item 60. The seal assembly, system, or method of any one of thepreceding items, wherein the spring comprises a metal.

Item 61. The seal assembly, system, or method of any one of thepreceding items, wherein the spring is die-formed from an overlappedmetal strip and configured with U-shaped cantilevers.

Item 62. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has a generally rectangularcross-section.

Item 63. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has an inner diameter ID₂ of atleast 80 mm, at least 85 mm, at least 90 mm.

Item 64. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has an inner diameter ID₂ of nogreater than 150 mm, no greater than 125 mm, or no greater than 115 mm.

Item 65. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has an inner diameter ID₂ of from80 to 150 mm, from 85 to 125 mm, from 90 to 115 mm.

Item 66. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has an inner diameter ID₂ that issubstantially the same as an inner diameter ID₁ of the seal body.

Item 67. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has a radial height RH₂ of atleast 1 mm, at least 2 mm, or at least 4 mm.

Item 68. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has a radial height RH₂ of nogreater than 12 mm, no greater than 10 mm, or no greater than 8 mm.

Item 69. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has a radial height RH₂ in arange of 1 to 12 mm, 2 to 10 mm, or 4 to 8 mm.

Item 70. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has a radial height RH₂ that issubstantially the same as a radial height RH₁ of the seal body.

Item 71. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has a ratio of radial height RH₂to inner diameter ID₂ of at least 1:30, at least 1:25, at least 1:20, orat least 1:15.

Item 72. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has a ratio of radial height RH₂to inner diameter ID₂ of no greater than 1:5, no greater than 1:7, or nogreater than 1:10.

Item 73. The seal assembly, system, or method of any one of thepreceding items, wherein the seal body has a ratio of radial height RH₂to inner diameter ID₂ in a range of 1:30 to 1:5, 1:25 to 1:7, or 1:20 to1:10.

Item 74. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has a ratio of radial height RH₂to inner diameter ID₂ that is substantially the same as a ratio ofradial height RH₁ to inner diameter ID₁ of the seal body.

Item 75. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has a first major surfacedefining an inner diameter, the first major surface adapted to engage ashaft and perform a sealing function.

Item 76. The seal assembly, system, or method of item 71, wherein thefirst major surface of the seal ring includes at least one seal groovethat extends radially along the first major surface of the seal ring.

Item 77. The seal assembly, system, or method of item 72, wherein the atleast one seal groove has opposing asymmetric sidewalls that extend intothe thickness of the seal ring.

Item 78. The seal assembly, system, or method of any one of items 71-73,wherein the first major surface includes at least two seal grooveshaving bilateral symmetry with each other.

Item 79. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has a contact surface that facesthe seal body.

Item 80. The seal assembly, system, or method of item 75, wherein thecontact surface is substantially orthogonal to a central axis of theseal ring.

Item 81. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has an axial height A_(H2) ofleast 1 mm, at least 1.5 mm, or at least 2 mm.

Item 82. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has an axial height A_(H2) of nogreater than 6 mm, no greater than 5 mm, or no greater than 4 mm.

Item 83. The seal assembly, system, or method of any one of thepreceding items, wherein the seal ring has an axial height A_(H2) in arange of 1 to 6 mm, 1.5 to 5 mm, or 2 to 4 mm.

Item 84. The seal assembly, system, or method of any one of thepreceding items, wherein the seal assembly is adapted to provide adynamic seal between the housing and the shaft, the dynamic seal havinga leakage rate of no greater than 0.05 mL per flight cycle for at least2000 simulated flight cycles, at least 3000 simulated flight cycles, atleast 4000 simulated flight cycles, at least 5000 simulated flightcycles, at least 10000 simulated flight cycles, at least 15000 simulatedflight cycles, or at least 20000 simulated flight cycles according to aFlight Cycle Test.

Item 85. The method of any one of the preceding items, wherein disposingthe seal assembly in the recess of the bore for sealing between thehousing and the shaft includes:

providing an installation tool set including a sleeve, a plug, and apusher.

Item 86. The method of item 74, wherein disposing the seal assembly inthe recess of the bore for sealing between the housing and the shaftfurther includes:

compressing the seal body into an oval shape and inserting the ovoidseal into the sleeve.

Item 87. The method of item 75, wherein disposing the seal assembly inthe recess of the bore for sealing between the housing and the shaftfurther includes:

inserting the pusher into the sleeve and push the seal body against theplug until the seal body is disposed in the recess of the bore of thehousing.

Item 88. A hydraulic strut comprising the system or seal assembly of anyone of the preceding items.

Item 89. An aircraft landing gear subcomponent comprising the sealassembly of any one of the preceding items.

Item 90. The seal assembly, system, or method of any one of thepreceding items, wherein the seal assembly is adapted for a hydraulicstrut having a bore including a groove adjacent the seal assembly grooveon a low pressure atmospheric side of the bore.

EXAMPLES Example 1

An embodiment of the seal assembly described herein was tested andcompared to a conventional seal assembly. Comparative Sample 1 was aconventional seal assembly (available under the trade name Turcon HatSeal II from Trelleborg Sealing Solutions in Fort Wayne, Ind.), whichincludes a molded elastomer ring that energizes apolytetrafluoroethylene (PTFE) platform. Sample 2 was an embodiment ofthe seal assembly described herein including a seal body, a spring, anda seal ring. The seal body comprised a fluorplastic material availableunder the trade name Fluoroloy A21 (from Saint-Gobain PerformancePlastics in Garden Grove, Calif.), the spring comprised a metal materialavailable under the trade name Egiloy (from Saint-Gobain in GardenGrove, Calif.), and the seal ring comprised a fluoroplastic materialavailable under the trade name Fluoroloy A68 (from Saint-GobainPerformance Plastics in Garden Grove, Calif.).

Each of the Comparative Sample 1 and Sample 2 had a radial height ofabout 0.2 inches and an inner diameter of about 3.7 inches, and weresubjected to the Flight Cycle Test described above. The results of thetests are described below in Table 2.

TABLE 2 Sample Leakage Rate Cycles Completed Comparative Sample 1 0.011mL/cycle 1100 Sample 2 0.0057 mL/cycle 20000

As shown by the results listed in Table 2, the seal assembly accordingto an embodiment of the seal assembly described herein was able tocomplete almost 20 times more cycles than the conventional sealassembly. In addition, the seal assembly according to an embodiment ofthe seal assembly described herein completed those cycles with abouthalf the leakage rate of the conventional seal assembly.

Example 2

Example 2 tests the installation of sample seal assemblies in thehydraulic strut of the Nose Landing Gear for the Airbus A318-A320aircrafts (strut available from Messier-Bugatti-Dowty inVélizy-Villacoublay, France) having multiple grooves and an bore depthof approximately 5 inches.

Samples 3 and 4 are substantially the same seal assembly as Sample 2 ofExample 1. Sample 3 is installed using traditional methods, such as bybending, folding, pushing down the bore and fitting into a groove byhand aided by pry bar. Sample 4 is installed using the tooling andinstallation method of this disclosure.

Sample 3 exhibits a crease in the seal body and the spring is deformedfrom the twisting required to install the seal assembly. In addition,the groove in the strut adjacent the installation groove and its sharpedges engage and damage the seal body. The damage to the seal assemblyindicates that the Sample 3 installation fails.

Sample 4 shows no signs of damage on the seal body or the spring. Theseal assembly is not twisted and does not engage the adjacent grooves ofthe strut. The lack of damage to the seal indicates that the Sample 4installation passes.

Note that not all of the activities described above in the generaldescription or the examples are required, that a portion of a specificactivity may not be required, and that one or more further activitiesmay be performed in addition to those described. Still further, theorder in which activities are listed is not necessarily the order inwhich they are performed.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any feature(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature of any or all the claims.

The specification and illustrations of the embodiments described hereinare intended to provide a general understanding of the structure of thevarious embodiments. The specification and illustrations are notintended to serve as an exhaustive and comprehensive description of allof the elements and features of apparatus and systems that use thestructures or methods described herein. Separate embodiments may also beprovided in combination in a single embodiment, and conversely, variousfeatures that are, for brevity, described in the context of a singleembodiment, may also be provided separately or in any subcombination.Further, reference to values stated in ranges includes each and everyvalue within that range. Many other embodiments may be apparent toskilled artisans only after reading this specification. Otherembodiments may be used and derived from the disclosure, such that astructural substitution, logical substitution, or another change may bemade without departing from the scope of the disclosure. Accordingly,the disclosure is to be regarded as illustrative rather thanrestrictive.

What is claimed is:
 1. A system for linear motion, comprising: a housinghaving a bore with an axis and a blind recess located in the bore; ashaft located in the bore for axial motion relative thereto; a sealassembly comprising a plastic polymer material located in the blindrecess of the bore adapted to provide a dynamic seal between the housingand the shaft, wherein the ratio of a radial height RH₁ of the sealassembly to an inner diameter ID₁ of the seal assembly is less than1:20.
 2. The system for linear motion of claim 1, wherein the sealassembly includes: a seal body comprising a first material; and a springdisposed adjacent to the seal body.
 3. The system for linear motion ofclaim 2, wherein the axial height of the seal body AH₁ is equal to thetotal axial height AH_(T) of the seal assembly.
 4. The system for linearmotion of claim 2, wherein the seal assembly further includes a sealring comprising a second material, wherein (1) each of the first andsecond materials comprises a plastic polymer material having a Young'smodulus of at least 150 MPa or (2) the first and second materials arethe same.
 5. The system for linear motion of claim 2, wherein the firstmaterial comprises a nylon, a fluoroplastic, a polybenzimidazole (PBI),a polyether ether ketone (PEEK), a polyaryletherketone (PAEK), apolyimide (PI), or any combination thereof.
 6. The system for linearmotion of claim 5, wherein the first material comprises a fluoroplasticincluding a polytetrafuoroethylene (PTFE), a perfluoroalkoxy (PFA), afluorinated ethylene propylene (FEP), a modified PTFE (TFM), an ethylenetetrafluoroethylene (ETFE), a polychlorotrifluoroethene (PCTFE), or anycombination thereof.
 7. The system for linear motion of claim 2, whereinthe first material has a Young's Modulus in a range of 150 to 1500 MPa.8. The system for linear motion of claim 4, wherein the second materialcomprises a nylon, a fluoroplastic, a PBI, a PEEK, a PAEK, a PI, or anycombination thereof.
 9. The system for linear motion of claim 8, whereinthe first material comprises a fluoroplastic including apolytetrafuoroethylene (PTFE), a perfluoroalkoxy (PFA), a fluorinatedethylene propylene (FEP), a modified PTFE (TFM), an ethylenetetrafluoroethylene (ETFE), a polychlorotrifluoroethene (PCTFE), or anycombination thereof.
 10. The system for linear motion of claim 4,wherein the second material has a Young's Modulus in a range of 150 to1500 MPa.
 11. The system for linear motion of claim 4, wherein the firstmaterial and the second material are the same.
 12. The system for linearmotion of claim 4, wherein the Shore D Hardness of the second materialis less than the Shore D Hardness of the first material.
 13. The systemfor linear motion of claim 4, wherein the first material is free of anelastomer, the second material is free of an elastomer, or both thefirst material and the second material are free of an elastomer.
 14. Thesystem for linear motion of claim 4, wherein the seal body has a contactsurface that faces the seal ring.
 15. The system for linear motion ofclaim 2, wherein the seal body has a ratio of radial height RH₁ to innerdiameter ID₁ in a range of 1:30 to 1:5.
 16. The system for linear motionof claim 2, wherein the seal body or seal ring has a first major surfacedefining an inner diameter, the first major surface adapted to engage ashaft and perform a sealing function.
 17. A method of installing a sealassembly, comprising providing a housing having a bore with an axis anda blind recess located in the bore; disposing a seal assembly comprisinga plastic polymer material in the blind recess of the bore; disposing ashaft in the bore for axial motion relative thereto; wherein the ratioof a radial height of the seal assembly to an inner diameter of the sealassembly is less than 1:20.
 18. The method of claim 17, whereindisposing the seal assembly in the recess of the bore for sealingbetween the housing and the shaft includes: providing an installationtool set including a sleeve, a plug, and a pusher.
 19. The method ofclaim 18, wherein disposing the seal assembly in the recess of the borefor sealing between the housing and the shaft further includes:compressing the seal body into an oval shape and inserting the ovoidseal into the sleeve.
 20. The method of claim 19, wherein disposing theseal assembly in the recess of the bore for sealing between the housingand the shaft further includes: inserting the pusher into the sleeve andpush the seal body against the plug until the seal body is disposed inthe recess of the bore of the housing.